title: Functional biomarkers of musculoskeletal syndrome (MSS) for early in vivo screening of selective MMP-13 inhibitors.
abstract: BACKGROUND
  Long-term administration of non-selective matrix metalloproteinase (MMP) inhibitors, such as marimastat, in humans elicits musculoskeletal syndrome (MSS), a syndrome characterized by joint damage including pain, stiffness, and inflammation. This pathology is a significant obstacle to the clinical development of MMP inhibitors and in pre-clinical models MSS can be verified only after terminal histopathology. Consequently, we devised a longitudinal and functional readout of MSS in conscious rats treated with marimastat that was validated against terminal histological assessment.
  
  
  METHODS
  MSS was induced by minipump infusion of marimastat (5-10mg/kg/day). In marimastat-treated or vehicle-control groups, three possible functional biomarkers were assessed: paw volume (PV), landing foot splay separation (LFSS), and rotarod performance (n=6 rats/group for each endpoint).
  
  
  RESULTS
  Histologically, fibrosis scores in the synovium and ligament increased from 0 on Day 1 (D1) to 4.6±0.2 and 4.7±0.1, respectively, on D15; growth plate thickness was also elevated from 215.0±6.3μm (D1) to 253.3±8.0μm (D15). While neither PV nor LFSS were correlative with MSS histopathology, marimastat (10mg/kg/day) reduced rotarod performance from 180±0s (D0) to 135±30s (D9) using a constant speed protocol (10rpm, 180s) and from 180±0s (D0) to 96±6s (D6) employing a variable speed protocol (increasing from 5 to 25rpm over 180s).
  
  
  CONCLUSIONS
  Results of the present study demonstrate that rotarod performance can be used as a predictive longitudinal, in vivo functional biomarker of MSS concomitant with histological evidence of joint damage to effectively facilitate compound selection during drug discovery. Moreover, for targets with a mechanistic risk for MSS, the model is also conducive to inclusion in secondary pharmacodynamic studies during lead optimization to identify the best (safest) compounds for advancement into clinical trials.
authors.affiliation: Boehringer Ingelheim Pharmaceuticals, Inc., United States. suzanne_nodop.mazurek@boehringer-ingelheim.com
authors.forename: Suzanne G Nodop
authors.initials: SG
authors.lastname: Mazurek
authors.forename: Jun
authors.initials: J
authors.lastname: Li
authors.forename: Gerald H
authors.initials: GH
authors.lastname: Nabozny
authors.forename: Glenn A
authors.initials: GA
authors.lastname: Reinhart
authors.forename: Akalushi C
authors.initials: AC
authors.lastname: Muthukumarana
authors.forename: Paul C
authors.initials: PC
authors.lastname: Harrison
authors.forename: Ryan M
authors.initials: RM
authors.lastname: Fryer
mesh_terms: D000818:Animals; D054316:Biomarkers, Pharmacological / Q000032:analysis; D004353:Drug Evaluation, Preclinical / Q000379:methods; D004791:Enzyme Inhibitors / Q000494:pharmacology* / Q000633:toxicity; D006877:Hydroxamic Acids / Q000494:pharmacology* / Q000633:toxicity; D007596:Joints / Q000187:drug effects / Q000473:pathology; D008137:Longitudinal Studies; D008297:Male; D061965:Matrix Metalloproteinase Inhibitors; D009140:Musculoskeletal Diseases / Q000139:chemically induced / Q000175:diagnosis / Q000473:pathology; D009141:Musculoskeletal System / Q000187:drug effects / Q000473:pathology; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D054316:Biomarkers, Pharmacological; D004791:Enzyme Inhibitors; D006877:Hydroxamic Acids; D061965:Matrix Metalloproteinase Inhibitors; C100342:marimastat